Method of preparing concrete



Patented Nov. 24, 1931 UNITED ST OFF METHOD PREPARING, ;C.0NCRETE NoDrawing.

Our invention relatesto the artof'malringj concrete and hasfor itsobject the provisionof an. improved methodor process of'preparing thesame to insure itsproper strength"- after hardening or setting. 1 Theinvention consists in regulatingthe amount or proportion; of moisture ina given quantity of miX- tnre by the removal of substantially all excessfree molsture from the mass after the mixing operation has-beenperformedfand lVith a view to aclearer,understandingpf the presentmodeof treatment and its etlect, some preliminary observations as to theusual practices in making., concrete are desirable. The quantities ofthevarious solid ingredients, includingicement and inert matter, em

ployed. in preparing a mixture .fora defin te Work orstructure areusually fixed upon "in advance of the undertaking, each being as signeda definite relative'proportion or value in termsusually of bulk orWeight, this estiao mate .beingbased. upon common experience.-Comparatively slight consideration is given in any given undertakingtothe correct rela;- tive proportion of fwater employed for effectingthe necessary chemical chang'e :in th'ecement togive ittheproperstrengtln Too much or-too little Water .are1bothldetrimental tothedesiredfresult, itibeingralvvays self evident that insufficient.moisture Would. fail in eliecting the chemical change inthe pow- 49dered cement necessary to give itzadhesive strengthand solidifyingproperties, whileit is now increasingly appreciatedlby those. engagedwith the commercial use .offfconcrete that any large excess of water isalso destruc'- As a, corrective ,i measure tive in its effect.

the quantity v of. Water supplied .the .mixing chamber is only roughlyestimated 7 with respect to the volume of the :solidiingrediientsemployed, irrespective oftheir characterano condition. The results,whileepartiallycon Applicationifiled;October:1, 1930. SeriaI'No.485,658.

rective in many instances, are notnniformly soand ifarffromapproximating iscientifieac-j curacy and dependability. This isattributed tothe factthat'moisture is always presemxto aVaryingQeXtentinor on'the inert-"matter as" usedin commercial practice, and it cannotPracticably be determined in advance of the actual mixing; operationWhat is the" proper quantity of water to'be used in eachiindiv'idnalmixture;

i From laboratory tests of "samples of dif ferent batches taken from thesame const-ruo-v tion job, alike in so far as therelative propor tionsof solid matter are involved butdifir ing in the content'ofwater',it'h'as been shown that'the compressive strength of the mass" after'like'periods of setting sh'ovv a'variance' sometimes amounting'to 50%,the resultant product in some instances being belowthat required forsafety and durability,

While commercial practices do not favor tl eattainment of absoluteaccuracyin ap portioning materials in making concrete, a reasonablerange" of variation, whilerelag tively smallin correct practice, ispermis'sible in the. proportion of water to th'e remain ing ingredientsfor 'difler'ent batchesfionzth'e'; same job. Keep'ingi within" the'-allowable range ofvariation', We have discovered, can bestoeattained-by" removing the excessfree moisture from eachbatch;separately'fafter' the .mixing operation :has been substantiallycomlfletedand'whilelthe "mass is still in a' fluid fsta-te, preliminaryto setting or 'hard'eni-i ing; The removal 'of this excess moisture mayb'e accomplished with practical success in various Ways such as;forexa'mple, by centrifuging,f"absorption, filtration, etcJ, ora'combination thereof.

In practicing our method or 1 process of making concrete, anintimate'mixture 'ofce ment', suchas Portland'cement or othemutosolidifying substance, with an aggregate comprising one or more inertsubstances such as sand and/or gravel, in" the pres; enoe of'Water,jsupp1ied in accordancewith any usual or approvednformula, s uch,fo1"v example, astwo'parts bygvolume of sandran'd: four parts; of gravelto-onei art of cement,"

with sufficient"water'-to rea ilyformamo hesive fluid mass, is firstmade up in the usual manner. The mixing operation may be performedeither by hand or with machinery, including any suitable mixing devices.

5 And while it is indispensable to the production of a good quality ofconcrete that approved practices regarding the use of ingredients ofapproved character, in proper proportion and properly mixed be observed,

our improvements in the art are more directly concerned with thecondition and treatment of concrete in the mixed mass while in a fluidstate, than with the mixing operation itself.

. It is not essential to the utility of our method that the quantity ofwater employed in the mixture during the mixing operation be accuratelymeasured before introduction to ,,the mixing chamber. It may evenlargely exceed the amount necessary to properly hydrate the cement. Noris it necessary that the inert ingredients be heated or otherwise driedout before introduction to the mixing chamber. It is, however, importantthat the mixing operation be substantially fully performed beforecommencement of the operation of removing the excess water, in order toinsure the thorough conversion of the re- .ment from an inert to anactive state, and that after such conversion the excess water in andthroughout the mixture be removed before the cement sets. By the termexcess water we refer to that portion of the total volume of water ormoisure present in the mixed mass which, if not removed at or before thecommencement of setting or hardening of the mass, impairs the strengthand quality of the concrete after setting, such excess beingsubstantially that portion of the water not required to properly hydratethe cement and to moisten the inert matter preliminary to hardening orplacing of the concrete.

In carrying out our invention we provide a suitable receptacle, whichmay be of any convenient size or shape, to receive the concrete afterthe mixing operation has been fully or subtantially performed. It is notessential to the successful application of our invention that theoriginal mixing chamber or apparatus be used for this purpose, althoughit may conveniently serve, nor that the entire mass be uniform indensity or in water content with respect to itself or other batches.

We prefer, in fact, to employ a separate receptacle of suitableproportions and conveniently arranged to readily accommodate periodicdischarges from the mixing apparatus or other source of supply. lVithinthis ultimate receptacle are placed or provided suitable water removingmeans, as, for example,

a pipe or conduit (not shown) having an inlet and provided with afiltering nozzle extending into the body of the mixture and an outletend extending beyond the mixture and connected to suitable mechanism forproducing suction of a predetermined strength adequate to remove theexcess moisture within and throughout the mixture but none of themoisture required to fully hydrate the cement and moisten the inertsubstances. Said filtering nozzle should be designed to effectivelyreach and drain substantially all parts of the interior, including theentire mass of concrete contents, of excess moisture.

Although a substantial portion of the excess water may rise to thesurface of the mass if the latter be permitted to stand undisturbed asufficient length of time, whether this result be accomplished bygravity alone or in conjunction with tamping or other artificial means,this gravitational or settling method is found to be unnecessarilytimetaking, deficient in thoroughness and otherwise objectionable. Byour present method or means the entire mass mixture is penetrated anddrained simultaneously and thoroughly before commencement of thehardening or setting of the concrete.

In the application of our improved method or process of preparingconcrete it is important that the dewatering operation, by whatevermeans effective for the ends described this be accomplished, should becommenced, adequately performed and fully completed within certainlimitations in point of time namely, immediately or shortly after theexposed or accessible surfaces of all particles of inert materials havebecome moistened and the entire body of cement or other auto-solidifyingsubstance has been completely hydrated, and before the latter hasappreciably begun to set or harden. It is equally important that thedewatering operation be extended to all parts of the mixture, as wellwithin and throughout the same as the exposed surfaces. It should befurther pointed out that whatever means are employed for removal of theexcess moisture, it is important also that the coercive force appliedshould be so regulated or controlled that only the excess moisture, andnone of the moisture necessary to moisten the inert matter and fullyhydrate the cement, be remove It will be understood that our inventionis not restricted to the precise details of the operations hereindescribed but embraces 0bvious modifications thereof, and iscommensurate with the scope of the appended. claims.

lVe claim as our invention:

1. The method of preparing concrete, consisting of intimately mixing anauto-solidifying substance with an aggregate, in the presence of water,then allowing the autosolidifying substance to become hydrated, andthereupon applying dewatering means to exert a coercive force tending toextract excess water from the mixture said force being regulated andapplied to and throughout the body of the mixture.

Ill)

2. The method of preparing concrete, consisting of intimately mixing anauto-soliditying substance with an aggregate, in the presence of waterthen allowing the autosoliditying substance to become fully hydrated,and then applying suctional dewatering means to all parts of the mixtureto remove the excess water before the mixture has begun to harden.

3. The method or process of preparing concrete, consisting of intimatelymixlng an auto-solidifying substance with an aggregate consisting of oneor more inert substances, in the presence of water, then allowing theauto-solidifying substance to become fully hydrated, and thereuponremoving the excess water by dewatering means adapted to exert apredeterminable extractive force applied throughout the mixture.

4,. The method or process of preparing concrete, consisting ofintimately mixing an auto-solidifying substance with an aggregate,consisting of one or more inert substances, in the presence of water,then allowing the auto-solidifying substance to become fully hydrated,and thereupon filtering and removing excess moisture from the mixed massby suctional means.

5. The method or process of preparing concrete, consisting of intimatelymixing an auto-solidifying substance with an aggregate consisting of oneor more inert substances, in the presence of water, then allowing themixture to remain undisturbed for a limited period of time, andthereupon removing the excess water from the mixed mass by means offiltration involving suction.

6. The method or process of preparing concrete, consisting of intimatelymixing an auto-solidifying substance with an aggregate, in the presenceof water, then allowing the auto-solidifying substance to become fullyhydrated, and then dewatering the mixture by removing the excessmoisture by filtration induced by suction havinga predetermined coerciveforce.

7. The method or process of preparing concrete, consisting of intimatelymixing an auto-solidifying substance with an aggregate, in the presenceof water, then allowing the auto-solidifying substance to become fullyhydrated, and then applying controlled dewatering means to exert aregulated extractive force to and throughout the mixture to remove onlythe excess water.

8. The method or process of preparing concrete, consisting of intimatelymixing an auto-solidifying substance with an aggre-o gate, in thepresence of water, then allowing the auto-solidifying substance tobecome fully hydrated, and then dewatering the mixture by filtrationinduced by suction having only suflicient coercive force to remove allthe moisture in excess of requirements for moistening the aggregatematerial and for fully hydrating the auto-solidifying substance.

In testimony whereof, we have signed our names to this specification.

MARTIN A. MORRISSEY. ALMER F. MOORE.

